Stroboscopic device

ABSTRACT

A provided flash unit includes a light emitting part in the main unit of the flash unit and a distance sensor provided only in the light emitting part, achieving an accurate measurement of a distance from a subject. In the flash unit according to the present invention, the light emitting part ( 10 ) includes a light receiving element ( 6 ) that measures reflected light when light is emitted in advance from the light emitting part ( 10 ) to a subject (T) and reflected light when light is emitted in advance from the light emitting part ( 10 ) to a reflector (X) for bounce photography, the flash unit determines and controls a proper tilt angle (θ 3 ) of the light emitting part ( 10 ) relative to a main unit ( 9 ) based on a distance (La) from the subject (T) and a distance (Lb) from the reflector (X), the distances being measured based on the detection by the light receiving element ( 6 ), and directivity for the detection by the light receiving element ( 6 ) is tilted toward the main unit ( 9 ) with respect to a horizontal direction.

FIELD OF THE INVENTION

The present invention relates to a flash unit that is mounted on acamera and emits light in stroboscopic photography.

BACKGROUND OF THE INVENTION

In stroboscopic photography of a subject with a flash unit mounted onthe accessory shoe of a camera, detection light emitted from a frontcentral part 3 of a main unit (the main unit of the flash unit) 9illustrated in FIG. 7 is reflected by the subject and the reflectedlight is detected by a distance measuring unit 4 disposed at the frontof the main unit 9. Subsequently, a distance between the flash unit 2and the subject is calculated based on the detection and then lightingis controlled such that a light emitting part 10 connected onto the mainunit 9 has a proper amount of light in final shooting.

Alternatively, in this case (in stroboscopic photography of the subjectwith the flash unit mounted on the accessory shoe of the camera),instead of the detection light emitted from the main unit 9, lightemitted in advance from the light emitting part 10 is reflected by thesubject and the reflected light is detected by the distance measuringunit 4 disposed at the front of the main unit 9. Subsequently, adistance between the flash unit 2 and the subject is calculated based onthe detection and then lighting is controlled such that the lightemitting part 10 has a proper amount of light in final shooting.

Stroboscopic photography includes direct photography in which the cameraand the light emitting part 10 of the flash unit are opposed to asubject and bounce photography in which the light emitting part 10,which is angled relative to the main unit 9, is not directly oriented tothe subject but is directed toward, for example, a ceiling surfaceserving as a reflector. In this case, in addition to a distance betweenthe camera and the subject, a distance between the flash unit and theceiling surface is measured while the camera and the flash unit 2attached to the camera are entirely opposed to the ceiling surfaceserving as a reflector. Subsequently, based on the distance between thecamera and the subject and the distance between the flash unit 2 and theceiling surface, lighting is controlled such that the light emittingpart 10 has a proper angle relative to the main unit 9 and has a properamount of light in final shooting.

Japanese Patent Laid-Open No. 2014-38268 discloses a technique in whichthe light emitting part 10 of the flash unit 2 is opposed to a subject Tas illustrated in FIG. 8A, a distance La from the subject T is measuredby a distance sensor 17 provided on the light emitting part 10, and thenthe light emitting part 10 is directed toward a ceiling surface X asillustrated in FIG. 8B so as to measure a distance Lb from the ceilingsurface X by the distance sensor 17 provided on the light emitting part10. As illustrated in FIG. 8C, lighting is controlled based on thedistance La and the distance Lb in bounce photography such that thelight emitting part 10 has a proper angle θ3 relative to the main unit 9and has a proper amount of light in final shooting.

As disclosed in Japanese Patent Laid-Open No. 2014-38268, a distance ismeasured by the distance sensor 17 provided on the light emitting part10, thereby eliminating the need for providing a sensor for measuring adistance on the main unit 9. Furthermore, a distance between the flashunit 2 and the ceiling surface X can be measured without entirelydirecting the camera 1 and the flash unit 2 attached to the camera 1toward the ceiling surface X.

In this case, however, when the light emitting part 10 of the flash unit2 is opposed to the subject T as illustrated in FIG. 8A and a distancefrom the subject T is measured by the distance sensor 17 provided on thelight emitting part 10, the distance La between the camera 1 and thesubject T cannot be accurately measured depending upon the position andsize of the subject relative to the angle of view of the camera.

An object of the present invention is to provide a flash unit that canaccurately measure a distance between a camera and a subject even if asensor for measuring a distance from the subject is provided only on alight emitting part attached to a main unit.

DISCLOSURE OF THE INVENTION

A flash unit according to the present invention is a flash unit thatautomatically controls the tilt of a light emitting part relative to amain unit during bounce photography, wherein the light emitting partincludes a distance measuring unit that measures reflected light whenlight is emitted in advance from the light emitting part to a subjectand reflected light when light is emitted in advance from the lightemitting part to a reflector for bounce photography, the flash unitdetermines and controls a proper tilt angle of the light emitting partrelative to the main unit based on a distance from the subject and adistance from the reflector, the distances being measured based on thedetection by the distance measuring unit, and directivity for thedetection by the distance measuring unit is tilted toward the main unitwith respect to a horizontal direction in a state in which the lightemitting part is directed toward the subject.

With this configuration, the directivity for the detection by thedistance measuring unit is tilted toward the main unit with respect tothe horizontal direction in a state in which the light emitting part isdirected toward the subject, thereby increasing the ratio of the area ofthe subject in the sensor range of the distance measuring unit ascompared with horizontal directivity for the detection by the distancemeasuring unit. In this way, accurate measurement of a distance betweenthe camera and the subject can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged cross-sectional view illustrating the principalpart of a light emitting part in a flash unit according to Embodiment 1of the present invention;

FIG. 2A is an external perspective view illustrating the flash unitaccording to the embodiment;

FIG. 2B is a front view of a light emitting part according to anotherembodiment;

FIG. 3A is an explanatory drawing illustrating a measurement of adistance La from a subject by the flash unit according to theembodiment;

FIG. 3B illustrates the position of emitted detection light in a screenin landscape orientation during a measurement of the distance La fromthe subject by the flash unit according to the embodiment;

FIG. 3C illustrates the position of emitted detection light in a screenin portrait orientation during a measurement of the distance La from thesubject by the flash unit according to the embodiment;

FIG. 4 is an enlarged cross-sectional view illustrating the principalpart of a light emitting part in a flash unit according to a comparativeexample in which a distance measuring sensor has horizontal detectiondirectivity;

FIG. 5A is an explanatory drawing illustrating a measurement of adistance La from a subject by the flash unit according to thecomparative example;

FIG. 5B illustrates the position of emitted detection light in a screenin landscape orientation during a measurement of the distance La fromthe subject by the flash unit according to the comparative example;

FIG. 6A is an explanatory drawing of photography in portraitorientation;

FIG. 6B illustrates the position of emitted detection light in a screenin portrait orientation during photography in portrait orientation;

FIG. 7 is an external perspective view illustrating an ordinary flashunit including a light receiving element in the main unit of the flashunit;

FIG. 8A is an explanatory drawing illustrating a measurement of adistance La from a subject by the ordinary flash unit including adistance sensor in the light emitting part of the flash unit;

FIG. 8B is an explanatory drawing illustrating a measurement of adistance Lb from a ceiling surface by the ordinary flash unit includingthe distance sensor in the light emitting part of the flash unit; and

FIG. 8C is an explanatory drawing illustrating bounce photography by theordinary flash unit including the distance sensor in the light emittingpart of the flash unit.

DESCRIPTION OF THE EMBODIMENT

Referring to FIGS. 1 to 6B, an embodiment of the present invention willbe described below.

FIGS. 1 to 3C illustrate Embodiment 1 of the present invention. FIGS. 4to 6B illustrate a comparative example.

Stroboscopic photography of a subject will be first described below. Aflash unit according to the embodiment is mounted on the accessory shoeof a camera that is set in landscape orientation as illustrated in FIG.3A.

As illustrated in FIG. 2A, a flash unit 2 according to the embodimentincludes a light emitting part 10 provided on a main unit (the main unitof the flash unit 2) 9. The light emitting part 10 has a light receivingwindow 5. As illustrated in FIG. 1, the light emitting part 10 containsa light receiving element 6 constituting a distance measuring unit.Detection light emitted in advance from the light emitting part 10 isreflected by a subject. The reflected light from the subject enters fromthe light receiving window 5, passes through a protective filter 7 and adiaphragm 8, and enters a light receiving part 11 of the light receivingelement 6. In the basic embodiment, the protective filter 7 does nothave lens characteristics that allow refraction of passing light.

The light receiving element 6 is disposed with horizontal directivity inthe light emitting part 10. However, the position and size of thediaphragm 8 are set relative to the light receiving element 6 such thata direction 15 of the looking angle of the distance measuring unitincluding the diaphragm 8 and the light receiving element 6 has an angleθ4 in a downward direction from a horizontal position. The downwarddirection viewed from the light emitting part 10 is a direction thatapproaches the main unit 9.

In contrast, in a comparative example of FIG. 4, the position and sizeof the diaphragm 8 are set relative to the light receiving element 6such that the looking angle of the distance measuring unit including thediaphragm 8 and the light receiving element 6 is located in thehorizontal position. Only this point is different from the embodiment.

In the comparative example where the distance measuring unit has alooking angle in the horizontal position as illustrated in FIGS. 5A and5B, the following problems occur: When the camera 1 is set in landscapeorientation, the light emitting part 10 is raised 90° as indicated by avirtual line in FIG. 5A and light is emitted in advance from the lightemitting part 10 of the flash unit 2 so as to accurately measure adistance Lb from a ceiling surface X serving as a reflector for bouncephotography. However, as indicated by a solid line in FIG. 5A, when thelight emitting part 10 of the flash unit 2 is opposed to a subject T andemits light in advance to measure a distance from the subject T, thedetection light of the light emitted in advance from the light emittingpart 10 is more likely to be reflected by a wall surface 12 behind thesubject T than by the subject T. P denotes the target position of theflash unit 2. In other words, the subject T has a small area ratio inthe sensor range of the light receiving element 6.

In the comparative example, an error Ld is likely to occur in ameasurement of a distance from the subject T and thus the flash unit 2frequently fails to automatically control the angle of the lightemitting part 10 to a proper angle during bounce photography.

Furthermore, in the comparative example, also when an image of thesubject T of FIG. 5A is to be captured by the camera 1 rotated 90° intoportrait orientation as illustrated in FIG. 6A, the target position P ofthe flash unit 2 is frequently displaced from the subject T to the wallsurface 12 as illustrated in FIG. 6B. Thus, also when the camera 1 isset in portrait orientation, the flash unit 2 frequently fails toautomatically control the angle of the light emitting part 10 to aproper angle during bounce photography.

In contrast, the diaphragm 8 in FIG. 1 illustrating the embodiment islocated closer to the main unit 9 than the diaphragm 8 (the position ofa virtual line 8J) for the light receiving element 6 in FIG. 4, that is,directivity for the detection by the distance measuring unit is tiltedtoward the main unit 9 with respect to a horizontal direction in a statein which the light emitting part 10 is directed toward the subject T.Thus, both in the landscape orientation and the portrait orientation ofthe camera 1, the distance Lb can be accurately measured as in thecomparative example when a distance from the ceiling surface X ismeasured. Moreover, when the camera 1 is set in landscape orientation asillustrated in FIGS. 3A and 3B, the target position P of the flash unit2 is located closer to the main unit 9, that is, lower in a screen inlandscape orientation. Hence, the detection light of light emitted inadvance from the light emitting part 10 of the flash unit 2 is morelikely to be reflected by the subject T than by the wall surface 12behind the subject T. Consequently, the target position P is more likelyto coincide with the subject T than in FIG. 5B, and thereby accuratemeasurement of the distance La from the subject T can be achieved. Inthis way, accurate measurement of the distance La from the subject T canbe achieved. Also when an image of the subject T of FIG. 5A is to becaptured alternatively in portrait orientation, as illustrated in FIG.3C, the target position P of the flash unit 2 in the embodiment islocated closer to the main unit 9, that is, inward in a screen inportrait orientation than in FIG. 6B. Consequently, the target positionP is more likely to coincide with the subject T than in FIG. 6B, andthereby accurate measurement of the distance La from the subject T canbe achieved.

In the embodiment, both in the landscape orientation and the portraitorientation of the camera 1, the distance La and the distance Lb can beaccurately measured with a high frequency. It is thus possible toincrease chances of success in automatic control of the angle of thelight emitting part 10 to a proper angle both in landscape orientationand portrait orientation during bounce photography compared to the casein the comparative example.

In the embodiment of FIGS. 1 to 3C, the distance measuring unit includesthe light receiving element 6 and the diaphragm 8 and the lightreceiving element 6 is disposed in the light emitting part 10 such thatthe light receiving element 6 has horizontal directivity. The lightreceiving element 6 in the light emitting part 10 directed toward thesubject T may have downward directivity, that is, the light receivingelement 6 may be attached with directivity tilted toward the main unit 9with respect to the horizontal direction to the light emitting part 10.In this case, the need for the diaphragm 8 in the distance measuringunit can be eliminated.

In the embodiment of FIGS. 1 to 3C, the distance measuring unit includesthe light receiving element 6 and the diaphragm 8 and the lightreceiving element 6 is disposed in the light emitting part 10 such thatthe light receiving element 6 has horizontal directivity. If the lightreceiving element 6 and the diaphragm 8 are configured as in thecomparative example, the same effects can be obtained as in FIGS. 3A and3B by regulating the lens characteristics of the protective filter 7 soas to tilt the target position P of the distance measuring unit towardthe main unit 9. The insertion position of the protective filter 7 onthe optical path of light reflected into the light receiving element 6can be changed to a position between the diaphragm 8 and the lightreceiving element 6.

In the foregoing embodiment, the light receiving window 5 is located onthe upper right of a light emitting window 13 (see FIG. 2A) of the lightemitting part 10. The position of the light receiving window 5 is notlimited thereto. The light receiving window 5 may be provided at anylocation around the light emitting window 13, for example, on the upperleft of the light emitting window 13 or any one of positions indicatedby virtual lines under the light emitting window 13.

The setting of the looking angle in the horizontal position for thedistance measuring unit including the diaphragm 8 and the lightreceiving element 6 as in the comparative example of FIG. 4 isequivalent to the case where a direction 14 at the center of the flashcoverage of the light emitting part 10 and the direction 15 of thelooking angle of the distance measuring unit are both horizontal in theshooting pattern of FIG. 3A. From this point of view, the configurationof the foregoing embodiment can be also expressed such that thedirection 14 at the center of the flash coverage of the light emittingpart 10 and the direction 15 of the looking angle of the distancemeasuring unit are different from each other.

The present invention can contribute to improvement in the performanceof a camera for automated bounce photography.

1. A flash unit that automatically controls tilt of a light emittingpart relative to a main unit during bounce photography, wherein thelight emitting part includes a distance measuring unit that measuresreflected light when light is emitted in advance from the light emittingpart to a subject and reflected light when light is emitted in advancefrom the light emitting part to a reflector for bounce photography, theflash unit determines and controls a proper tilt angle of the lightemitting part relative to the main unit based on a distance from thesubject and a distance from the reflector, the distances being measuredbased on detection by the distance measuring unit, and directivity forthe detection by the distance measuring unit is tilted toward the mainunit with respect to a horizontal direction in a state in which thelight emitting part is directed toward the subject.
 2. The flash unitaccording to claim 1, wherein the distance measuring unit is a lightreceiving element that detects reflected light from the subject.
 3. Theflash unit according to claim 1, wherein the distance measuring unitincludes: a light receiving element that detects reflected light fromthe subject; and a diaphragm that limits an acceptance angle of lightreflected into the light receiving element.
 4. The flash unit accordingto claim 1, wherein the distance measuring unit includes: a lightreceiving element that detects reflected light from the subject; adiaphragm that limits an acceptance angle of light reflected into thelight receiving element; and a protective filter that has lenscharacteristics and is inserted on an optical path of light reflectedinto the light receiving element, and directivity for detection by thedistance measuring unit is tilted toward the main unit with respect to ahorizontal direction by the lens characteristics of the protectivefilter.
 5. A flash unit that automatically controls tilt of a lightemitting part relative to a main unit during bounce photography, whereinthe light emitting part includes a distance measuring unit that measuresreflected light when light is emitted in advance from the light emittingpart to a subject and reflected light when light is emitted in advancefrom the light emitting part to a reflector, the flash unit determinesand controls a proper tilt angle of the light emitting part relative tothe main unit based on a distance from the subject and a distance fromthe reflector, the distances being measured based on detection by thedistance measuring unit, and a direction at a center of a flash coverageof the light emitting part and a direction of a looking angle aredifferent from each other, the looking angle serving as directivity forthe detection by the distance measuring unit.
 6. The flash unitaccording to claim 5, wherein the direction of the looking angle istilted toward the main unit with respect to the direction at the centerof the flash coverage.